The present invention relates generally to vision testers and vision testing methods, and more particularly to a novel system and method for testing a plurality of human vision parameters.
Many astronauts have commented on apparent vision problems during earth orbit, including supposed "super-vision" by pre-Gemini astronauts, and, more recently, complaints including reduction in near visual acuity with no apparent change in distant vision, significant elevation of intraocular pressure, "misplaced horizon", and increased dependence upon reading glasses. Although the literature contains numerous reference to various anticipated effects of orbital environmental conditions upon human vision, few actual tests were performed since suitable instrumentation and testing methods have not heretofore existed for use in quantifying changes in all the numerous human vision parameters of interest under orbital conditions. The prior tests which were conducted included out-the-window visual acuity measurements using sightings of ground targets from Gemini V and VII, and a near-vision test series on accommodative amplitude performed on STS-5 and later flights.
The present invention comprises a compact, portable, and battery powered system and vision testing method for the rapid measurement of a plurality of human vision parameters, including critical fusion frequency, stereopsis. Snellen visual acuity and visual resolution, cyclophoria (torsional phoria), eye dominance (retinal rivalry), and lateral and vertical phoria. The visual function tester of the present invention combines a dual optical system with a broad spectrum of illuminated visual test patterns in a compact, portable unit which may find particular utility for the definition and measurement of the environmental and physiological effects on a broad range of human vision parameters, such as changes in these parameters under the effects of orbital space flight.
The system of the present invention is self powered and uses microelectronic circuitry controlled light emitting diode (LED) displays to create a series of controlled illumination stimulus patterns at or near optical infinity, for use in measuring a plurality of visual functions, with a separate stimulus pattern or set of patterns configured for testing each such visual function. The unique arrangement of all test patterns within the same field of view allows each pattern to be used by electronically switching the appropriate LED, thus eliminating the need for any mechanical moving parts with the exception of the switch. This improves the optical alignment and ruggedness of the system as there are no moving parts to wear or become misaligned. Data may be recorded verbally by the subject on a microcassette audio recorder which may be included as a part of the electronics of this system; the subject may indicate verbally the test number and observed results as shown in the vision function tester.
It is, therefore, a principal object of the present invention to provide a novel portable visual function tester and method for measuring a plurality of human vision parameters, including critical fusion frequency, stereopsis. Snellen visual acuity and visual resolution, cyclophoria (torsional phoria), eye dominance (retinal rivalry), and lateral and vertical phoria.
It is a further object of the present invention to provide a visual function tester for measuring the environmental effects on the various named human vision parameters.
It is a further object of the invention to provide a system and method for quantifying changes in certain human vision parameters under the effects of orbital space flight.
It is still another object of the invention to provide a method for testing the effects of various environmental conditions on the named human vision parameters.
These and other objects of the present invention will become apparent as the detailed description of certain representative embodiments thereof proceeds.